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From:   Roger He <Hongbo.He@amd.com>
To:     <dri-devel@lists.freedesktop.org>
CC:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        <Christian.Koenig@amd.com>, Roger He <Hongbo.He@amd.com>
Subject: [PATCH] mm/swap: add function get_total_swap_pages to expose total_swap_pages
Date:   Mon, 29 Jan 2018 16:29:42 +0800
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ttm module needs it to determine its internal parameter setting.

Signed-off-by: Roger He <Hongbo.He@amd.com>
---
 include/linux/swap.h |  6 ++++++
 mm/swapfile.c        | 15 +++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index c2b8128..708d66f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -484,6 +484,7 @@ extern int try_to_free_swap(struct page *);
 struct backing_dev_info;
 extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
 extern void exit_swap_address_space(unsigned int type);
+extern long get_total_swap_pages(void);
 
 #else /* CONFIG_SWAP */
 
@@ -516,6 +517,11 @@ static inline void show_swap_cache_info(void)
 {
 }
 
+long get_total_swap_pages(void)
+{
+	return 0;
+}
+
 #define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
 #define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
 
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 3074b02..a0062eb 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -98,6 +98,21 @@ static atomic_t proc_poll_event = ATOMIC_INIT(0);
 
 atomic_t nr_rotate_swap = ATOMIC_INIT(0);
 
+/*
+ * expose this value for others use
+ */
+long get_total_swap_pages(void)
+{
+	long ret;
+
+	spin_lock(&swap_lock);
+	ret = total_swap_pages;
+	spin_unlock(&swap_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(get_total_swap_pages);
+
 static inline unsigned char swap_count(unsigned char ent)
 {
 	return ent & ~SWAP_HAS_CACHE;	/* may include SWAP_HAS_CONT flag */
-- 
2.7.4